JP2016024951A - Solid-state oxide fuel battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state oxide fuel battery in which the electrical connection between layers can be kept even when exfoliation between the layers upon application of a thermal cycle or the like, and thus reliability of the electrical connection can be enhanced.SOLUTION: In a solid-state oxide fuel battery 1, plural solid oxide type fuel battery cells 2 are stacked, and at a portion where the fuel battery cells 2, 2 are stacked, a metal layer 10 is disposed between one fuel battery cell 2 and the other fuel battery cell 2, and plural minute electrically conductive layers 11 for electrically connecting the fuel battery cell and the metal layer, and porous electrically conductive layers 11b are combined and arranged alternately in parallel side by side at a connection face on the fuel battery cell 2 side and at a connection face on the metal layer 10 side.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a solid oxide fuel cell in which a plurality of solid oxide fuel cells are stacked.

A solid oxide fuel cell (also referred to as SOFC: Solid Oxide Fuel Cell) is a fuel electrode (anode): H ₂ + O ²⁻ → H ₂ O + 2e ⁻ , an air electrode (cathode): (1 / 2) A device for extracting electric energy by a reaction of O ₂ + 2e ⁻ → O ²⁻ . In order to continuously extract electric energy, it is necessary to perform the reaction continuously. Therefore, oxidation of fuel gas (for example, H ₂ ) as an anode gas and air (O ₂ ) as a cathode gas supplied to the cathode is performed. The agent gas is continuously supplied. In a solid oxide fuel cell, a plurality of fuel cells are stacked in order to obtain a sufficient voltage. Thereby, a fuel cell (fuel cell stack) is configured. Fuel cell stacks can be fabricated by co-sintering ceramics, but the anode gas flow path width and cathode gas flow path width have a specific relationship to prevent warpage resulting from thermal shrinkage behavior during firing. It has been proposed to provide such that (see, for example, Patent Document 1).

  In addition, since the thermal conductivity of ceramics is relatively low, if the number of fuel cell stacks using ceramics is increased, the heat generated by power generation tends to stay in the vicinity of the center of the fuel cell stack. For this reason, heat distribution is generated on the surface of the fuel cell, and there is a possibility that the cell is cracked due to thermal stress. On the other hand, a method of reducing nonuniformity of heat distribution by arranging a metal layer such as a metal film or a metal plate between cells is also known (see, for example, Patent Document 2).

JP 2009-252474 A JP 2006-310005 A

  In this case, the influence of thermal stress can be reduced. However, since the thermal expansion coefficients of the metal and the ceramic are considerably different, there is a possibility that separation between the metal and the ceramic occurs. And in the said method, since the electrical connection was achieved by the metal and ceramics contacting directly, when the above peeling occurred, there existed a problem that an electrical connection will be interrupted.

  The present invention solves the above-described problems, and even when peeling between layers occurs when a thermal cycle is applied, the electrical connection between the layers can be maintained, and the reliability of the electrical connection is improved. An object is to provide an enhanced solid oxide fuel cell.

In order to achieve the above object, the solid oxide fuel cell of the present invention has a structure in which a plurality of fuel cells are stacked. The solid oxide fuel cell of the present invention includes a plurality of stacked solid oxide fuel cells, and one fuel cell and the other fuel cell in a portion where the fuel cells are stacked. A conductive layer disposed between the metal layer and the fuel cell so as to electrically connect the metal layer and the fuel cell. With
The conductive material layer is configured by combining a dense conductive material layer made of a dense conductive material having a low porosity and a porous conductive material layer made of a porous conductive material having a high porosity,
The dense conductive material layer electrically connects the fuel cell and the metal layer,
The dense conductive material layer and the porous conductive material layer are arranged in parallel and alternately in a plurality on the connection surface on the fuel cell side and the connection surface on the metal layer side.

  In a specific aspect of the solid oxide fuel cell according to the present invention, between the porous conductive material layers, the dense conductive material layer has a gap in a direction connecting the fuel cell and the metal layer. Yes.

  In still another specific aspect of the solid oxide fuel cell of the present invention, a porous conductive material having a high porosity is disposed in the gap portion.

  In the solid oxide fuel cell of the present invention, the porosity of the porous conductive material is preferably in the range of 20 to 90%.

In the solid oxide fuel cell of the present invention, the porous conductive material _{is, LaSrMnO 3, LaSrCoO 3, LaSrCoFeO} 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, (LaSr) 2 NiO Preferably, the conductive ceramic is mainly composed of at least one material selected from the group consisting of _four .

  In the solid oxide fuel cell of the present invention, the dense conductive material preferably has a porosity in the range of 0 to 20%.

In the solid oxide fuel cell of the present invention, the dense conductive _{material, LaSrMnO 3, LaSrCoO 3, LaSrCoFeO} 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, (LaSr) 2 NiO 4 Conductive ceramics mainly composed of at least one material selected from the group consisting of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, Cr, and alloys mainly composed of these metals Preferably, the main component is at least one metal selected from the group consisting of:

  According to the solid oxide fuel cell of the present invention, even if a thermal cycle is applied and partial delamination occurs between the conductive material layer and the metal layer and / or the fuel cell, the fuel cell and the metal layer Since the dense conductive material layer that electrically connects the two is formed to extend in the surface direction on the connection surface, the conductive path itself is not lost. Therefore, the conductive material layer can maintain an electrical connection between the metal layer and the fuel battery cell. Therefore, the reliability of electrical connection can be improved.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

FIG. 1A is a schematic front cross-sectional view showing a main part of a fuel cell according to a first embodiment of the present invention. FIG.1 (b) is the top view which looked at the electrically-conductive material layer from the upper surface in Fig.1 (a). It is a disassembled perspective view of one fuel battery cell used for the fuel battery of the 1st Embodiment of this invention. It is a top view of one fuel battery cell used for the fuel battery concerning a 1st embodiment. 1 is a perspective view schematically showing a fuel cell according to a first embodiment. FIG. 5 is a cross-sectional view of the conductive material layer according to the first embodiment when viewed in the II direction in FIG. FIG. 6A is a plan view of the conductive material layer of the comparative example as viewed from above. FIG. 6B is a cross-sectional view of the conductive material layer of the comparative example as viewed in the II-II direction in FIG. FIG. 7 is a plan view of the conductive material layer used in the fuel cell according to the second embodiment of the present invention as seen from above. FIG. 8 is a plan view of the conductive material layer used in the fuel cell according to the third embodiment of the present invention as seen from above.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited or limited to the following examples. The drawings referred to below are schematically described, and the ratio of the dimensions of objects drawn in the drawings may be different from the ratio of dimensions of actual objects. The dimensional ratio of the object may be different between the drawings.

(First embodiment)
FIG. 1A is a schematic front sectional view of a fuel cell according to a first embodiment of the present invention. In the fuel cell 1, the upper fuel cell 2 and the lower fuel cell 2 are joined via a joint 4. Although FIG. 1A shows two fuel cells 2, 2, in the present embodiment, the structure in which the fuel cells 2, 2 on both sides are stacked via another joint 4. Are further lined up.

  Moreover, in Fig.1 (a), only the position in which the fuel cell 2 and 2 is provided is shown schematically. Details of one fuel cell 2 will be described with reference to FIGS. 2 and 3.

  As shown in FIG. 2, the fuel battery cell 2 has a solid oxide electrolyte layer 7. The solid oxide electrolyte layer 7 is made of a ceramic having high ionic conductivity. Examples of such materials include stabilized zirconia and partially stabilized zirconia. More specifically, zirconia stabilized by Y or Sc is mentioned. Examples of the stabilized zirconia include 10 mol% yttria stabilized zirconia (10YSZ) and 11 mol% scandia stabilized zirconia (11ScSZ). Examples of the partially stabilized zirconia include 3 mol% yttria partially stabilized zirconia (3YSZ).

Incidentally, the material constituting the solid oxide electrolyte layer 7 is not limited to the above, Sm and Gd-doped ceria-based oxide _{and, La 0.8 Sr 0.2 Ga 0.8 Me} 0.2 O You may form by perovskite type oxides, such as _(3-delta) . Δ represents a positive number less than 3.

  The solid oxide electrolyte layer 7 is provided with a through hole 7a and a through hole 7b. The through hole 7a constitutes a fuel gas flow path. The through hole 7b constitutes an air flow path through which air as an oxidant gas passes.

  A fuel electrode layer 6 is laminated above the solid oxide electrolyte layer 7. The fuel electrode layer 6 can be composed of yttria-stabilized zirconia containing Ni, scandia-stabilized zirconia containing Ni, or the like. The fuel electrode layer 6 is provided with a slit 6a constituting a fuel gas flow path and a slit 6b constituting an air flow path.

  A separator 5 is laminated on the fuel electrode layer 6. The separator 5 can be formed of stabilized zirconia, partially stabilized zirconia, or the like. Through holes 5 a and 5 b are formed in the separator 5. The through hole 5a constitutes a fuel gas flow path. The through hole 5b constitutes an air flow path.

  On the other hand, the separator 5 is provided with a plurality of interconnectors 5 c for taking out electricity so as to penetrate the lower surface from the upper surface of the separator 5. That is, each interconnector 5c is formed by a via-hole conductor. The plurality of interconnectors 5 c are electrically connected to the fuel electrode layer 6.

The material of the interconnector 5c is not particularly limited. The interconnector 5c includes, for example, an Ag—Pd alloy, an Ag—Pt alloy, lanthanum chromite (LaCrO ₃ ) added with an alkaline earth metal, lanthanum ferrate (LaFeO ₃ ), lanthanum strontium manganite (LSM). ) Or the like.

On the other hand, an air electrode layer 8 and a separator 9 are laminated below the solid oxide electrolyte layer 7. The air electrode layer 8 is provided with a slit 8a that constitutes a fuel gas passage and a slit 8b that constitutes an air passage. The air electrode layer 8 is preferably made of a porous material having high electron conductivity. Such an air electrode layer 8 includes, for example, scandia-stabilized zirconia (ScSZ), ceria doped with Gd, indium oxide doped with Sn, PrCoO ₃ oxide, LaCoO oxide, or LaMoO ₃ oxide. It can be formed by things. Examples of the LaMoO ₃ oxide include La _0.8 Sr _0.2 MnO ₃ (hereinafter abbreviated as LSM) and La _0.6 Ca _0.4 MnO ₃ .

  The separator 9 is configured similarly to the separator 5. Therefore, it has the through-hole 9a which comprises a fuel gas flow path, the through-hole 9b which comprises an air flow path, and the several interconnector 9c.

  The fuel battery cell 2 is prepared by mixing and molding the materials shown above with a binder and a solvent for each component, preparing a green sheet having a predetermined shape, and laminating and crimping these green sheets, It can obtain through the baking process integrated by co-sintering the obtained laminated body.

  FIG. 3 shows a plan view of the single fuel cell 2. As shown in FIG. 3, the fuel battery cell 2 has a cross-shaped flow path component 2a and four power generation units 2b, 2c, 2d, and 2e partitioned by the flow path component 2a when viewed in plan. . And the said interconnector 5c is exposed to the upper surface of the electric power generation parts 2b-2e.

  In the fuel cell 1 of the present embodiment, a plurality of such fuel cells 2 are stacked. FIG. 4 is a perspective view showing the fuel cell 1. As shown in FIG. 4, in the fuel cell 1, the fuel cells 2, 2, 2 are stacked via joints 4, 4.

  As shown in FIG. 1A, the fuel cell 1 according to the present embodiment is characterized by the structure of a joint 4 that joins the fuel cell 2 and the fuel cell 2.

  The joint 4 physically joins and integrates the upper fuel cell 2 and the lower fuel cell 2, and electrically connects the upper fuel cell 2 and the lower fuel cell 2 in series. Connected. The joint 4 is provided with a metal layer 10 so as not to concentrate heat in the center and to electrically connect the upper fuel cell 2 and the lower fuel cell 2.

  In the present embodiment, the metal layer 10 is made of a metal plate. The material constituting the metal plate is not particularly limited, but it is desirable to use a metal having a thermal expansion coefficient close to that of the ceramic constituting the fuel cell 2. As such a material, preferably, ferritic stainless steel can be used. The thermal expansion coefficient of ferritic stainless steel is close to that of zirconia. Ferritic stainless steel has excellent heat resistance. Accordingly, ferritic stainless steel is preferred.

  But the material which comprises the said metal layer 10 is not specifically limited, You may use another metal.

  Conductive material layers 11 are respectively provided on the upper surface and the lower surface of the metal layer 10. The conductive material layer 11 is disposed between the metal layer 10 and the fuel cell 2 so as to electrically connect the metal layer 10 and the fuel cell 2.

  The conductive material layer 11 is configured by combining a dense conductive material layer 11a made of a dense conductive material having a low porosity and a porous conductive material layer 11b made of a porous conductive material having a high porosity. As shown in FIG. 1A, the dense conductive material layer 11a and the porous conductive material layer 11b are arranged in parallel and alternately on the connection surface on the fuel cell 2 side and the connection surface of the metal layer 10. Has been placed. FIG.1 (b) is the top view which looked at the electrically conductive material layer 11 from the upper surface in Fig.1 (a). As shown in FIG. 1B, the dense conductive material layer 11 a is formed to extend in the surface direction on the connection surface with the fuel cell 2 and the connection surface with the metal layer 10. The dense conductive material layer 11a mainly serves to electrically connect the fuel cells 2 and the metal layer 10, and the porous conductive material layer 11b serves mainly to maintain the shape of the dense conductive material layer 11a. Fulfill.

  FIG. 5 is a cross-sectional view of the conductive material layer 11 as viewed in the II direction in FIG. For example, when a heat cycle is applied, separation may occur partially between the conductive material layer 11 and the metal layer 10 and / or the fuel cell 2. FIG. 5 shows a case where a partial peeling portion (void) 14 is generated between the conductive material layer 11 and the metal layer 10. Thus, even if the peeling portion 14 occurs between the conductive material layer 11 and the metal layer 10, the conductive path in the plane direction (Y-axis direction in the drawing) is maintained, so that the reliability of electrical connection Can be made higher.

  For comparison, in FIGS. 6A and 6B, a conductive material layer 21 is formed by a combination of a dense conductive material 21a and a porous conductive material 21b, and the dense conductive material 21a is formed on the top surface (FIG. A case (comparative example) in which dots are formed when viewed from the same direction as b) is shown. 6A is a plan view of the conductive material layer 21 as viewed from above, and FIG. 6B is a cross-sectional view of the conductive material layer 21 as viewed in the II-II direction in FIG. 6A. In the case of the conductive material layer 21 in which the portion responsible for electrical connection is formed in a dot shape, when the peeling portion 24 is generated between the conductive material layer 21 and the metal layer 10, conduction is partially interrupted. There is a case. Therefore, in the fuel cell 1, the dense conductive material layer 11 a and the porous conductive material layer 11 b are arranged in the plane direction on the connection surface between the dense conductive material layer 11 a and the metal layer 10 and / or the fuel cell 2 as described above. Therefore, the reliability of electrical connection can be effectively increased.

  In the case of the conductive material layer 21 having the configuration of FIG. 6, when a power cycle test (2000 hours, about 1000 cycles, ambient temperature about 750 ° C.) is performed, the deterioration rate is about 3%, for example. When the conductive material layer 11 having the configuration is used, the deterioration rate under the same condition can be suppressed to about 2%.

In the present embodiment, the material constituting the conductive material layer 11 is made of LaSrMnO ₃ (LSM: Lanthanum Strontium Manganite) which is a conductive ceramic material. The porous conductive material layer 11b can be formed by causing the LSM to contain a disappearing material such as carbon and sintering so that the disappearing material disappears during sintering. Thus, the dense conductive material layer 11a and the porous conductive material layer 11b can be formed by changing the denseness of the same material. Alternatively, the dense conductive material layer 11a and the porous conductive material layer 11b can be formed using different materials.

But the material which comprises the said electrically-conductive material layer 11 is not specifically limited, What is necessary is just to have favorable electroconductivity. For example, in the case of a conductive ceramic material, a material having a crystal structure of ABO ₃ or A ₂ BO ₄ (A: one kind of rare earth, B: one kind of transition element) can be mentioned. Specifically, the above-mentioned LSM, LaSrCoO ₃ , LaSrCoFeO ₃ , MnCoO ₃ , SmSrCoO ₃ , LaCaMnO ₃ , LaCaCoO ₃ , LaCaCoFeO ₃ , LaNiFeO ₃ , (LaSr) ₂ NiO _4, etc. can be used. Since these materials have electrical conductivity, the electrical resistance between the fuel cells can be reduced by using the conductive material layer 11, and the stack characteristics can be improved.

  The dense conductive material layer 11a is at least selected from the group consisting of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, Cr and alloys mainly composed of these metals in addition to the conductive ceramic material. It is also preferable that the main component is one kind of metal. Since these are materials having high conductivity, the electrical resistance between the cells can be reduced by using the dense conductive material layer 11a, and the stack characteristics can be improved. In this specification, “mainly” means to occupy 1/2 or more.

  The porosity of the porous conductive material is preferably in the range of 20 to 90%, more preferably in the range of 40 to 80%. Further, the porosity of the dense conductive material is most preferably 0%, but it may be in the range of 0 to 20%, preferably in the range of 0 to 10%. Here, the porosity means the porosity calculated in the state before sintering, and is a value defined by the ratio of the lost material volume to the total volume when the conductive material layer is formed.

  When the porosity of the porous conductive material is within the above range, it is possible to follow the unevenness of the fuel cell 2 and the metal layer 10 during stacking, which is preferable. Moreover, when the porosity of the dense conductive material is within the above range, the electrical conductivity can be increased, which is preferable.

  For example, the conductive material layer 11 may be obtained by co-sintering alternately stacked conductive ceramic sheets having different sinterability, or co-fired by alternately stacking conductive ceramic sheets and metal sheets. It can tie and produce.

The width of each layer constituting the conductive material layer 11 is such that the dense conductive material layer 11a is in the range of 0.1 to 0.5 mm, and the porous conductive material layer 11b is in the range of 0.3 to 1.0 mm. Is preferred. The ratio of the width of the dense conductive material layer 11a and the width of the porous conductive material layer 11b is preferably in the range of 1: 3 to 1:10. The higher the conductivity of the conductive material layer 11 is, the better the specific area resistance of the dense conductive material layer 11a is preferably 15 mΩcm ² or less, and the specific area resistance of the porous conductive material layer 11b is 20 mΩcm ² or less. Preferably there is.

  Furthermore, in the present embodiment, the bonding portion 4 is a laminated structure of the adhesive layer 12 and the spacer 13 in a region different from the bonding portion that electrically connects the power generation portions 2b, 2c, 2d, and 2e. Have Here, the spacer 13 does not necessarily need to be provided, but it is desirable to use the spacer 13 for facilitating adhesion when the distance between the fuel cells 2 and 2 is large. The material constituting the spacer 13 is not particularly limited, but a material having a thermal expansion coefficient close to that of the ceramic constituting the fuel cell 2 is desirable. Although the material which comprises the adhesive material layer 12 is not specifically limited, The material which expresses favorable adhesiveness between the fuel cell 2 and 2 or between the fuel cell 2 and the spacer 13 is desirable, for example, crystallized glass Etc. can be used.

  In the present embodiment, the solid oxide fuel cell 1 sandwiches the molded conductive material layer 11 and the adhesive material layer 12 between the fired fuel cell 2 (cell stack), the metal layer 10 and the spacer 13. It can obtain by performing heat processing in the state where the load was applied from above.

(Second Embodiment)
FIG. 7 is a plan view of the conductive material layer used in the fuel cell according to the second embodiment of the present invention as seen from above. In the present embodiment, the dense conductive material layer 11 a has a gap 15 in the direction connecting the fuel cell 2 and the metal layer 10 between the porous conductive material layers 11 b. That is, the dense conductive material layer 11a is not provided continuously from the end to the end of the porous conductive material layer 11b, but is arranged so as to be separated by a certain length. By setting it as such an aspect, it becomes possible to suppress generation | occurrence | production of the crack by the shrinkage | contraction at the time of sintering.

(Third embodiment)
FIG. 8 is a plan view of the conductive material layer used in the fuel cell according to the third embodiment of the present invention as seen from above. In the present embodiment, the dense conductive material layer 11a is provided with a gap 15 as in the second embodiment. A porous conductive material is disposed so as to correspond to the position of the gap 15. Thus, by disposing the porous conductive material made of conductive ceramics or the like on the portion formed by dividing the dense conductive material layer 11a, the dense conductive material layer 11a is fixed, and the reliability of electrical connection is further increased. Can be realized.

  In this way, by providing a conductive material layer that electrically connects the metal layer and the fuel cell, and making this conductive material layer have a specific structure, delamination between layers occurs when a thermal cycle is applied. Even so, it is possible to obtain a solid oxide fuel cell in which the electrical connection between the layers can be maintained and the reliability of the electrical connection is enhanced.

DESCRIPTION OF SYMBOLS 1 ... Fuel cell 2 ... Fuel cell 2a Flow path structure part 2b, 2c, 2d, 2e Power generation part 4 Joint part 5 Separator 5a, 5b Through-hole 5c Interconnector 6 Fuel electrode layer 6a, 6b Slit 7 Solid oxide electrolyte layer 7a, 7b Through hole 8 Air electrode layer 8a, 8b Slit 9 Separator 9a, 9b Through hole 9c Interconnector 10 Metal layer 11 Conductive material layer 11a Dense conductive material layer 11b Porous conductive material layer 12 Adhesive layer 13 Spacers 14, 24 Peeling portion 15 Gap 21 Conductive material layer 21a Dense conductive material 21b Porous conductive material

Claims (7)

A solid oxide fuel cell having a structure in which a plurality of fuel cells are stacked,
A plurality of stacked solid oxide fuel cells, and
In the portion where the fuel cells are stacked, a metal layer disposed between one fuel cell and the other fuel cell,
A conductive material layer disposed between the metal layer and the fuel cell so as to electrically connect the metal layer and the fuel cell;
The conductive material layer is configured by combining a dense conductive material layer made of a dense conductive material having a low porosity and a porous conductive material layer made of a porous conductive material having a high porosity,
The dense conductive material layer electrically connects the fuel cell and the metal layer,
The dense conductive material layer and the porous conductive material layer are arranged in parallel and alternately in a plurality on the connection surface on the fuel cell side and the connection surface on the metal layer side. Fuel cell. The solid oxide fuel cell according to claim 1, wherein the dense conductive material layer has a gap in a direction connecting the fuel cell and the metal layer between the porous conductive material layers. The solid oxide fuel cell according to claim 2, wherein a porous conductive material having a high porosity is disposed in the gap portion. The solid oxide fuel cell according to any one of claims 1 to 3, wherein a porosity of the porous conductive material is in a range of 20 to 90%. The porous conductive material _{is, LaSrMnO 3, LaSrCoO 3, LaSrCoFeO} 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, at least one selected from the group consisting of _(LaSr) 2 NiO ₄ 5. The solid oxide fuel cell according to claim 1, wherein the solid oxide fuel cell is a conductive ceramic mainly composed of the above material. The solid oxide fuel cell according to any one of claims 1 to 5, wherein a porosity of the dense conductive material is in a range of 0 to 20%. The dense conductive _{material, LaSrMnO 3, LaSrCoO 3, LaSrCoFeO} 3, MnCoO 3, SmSrCoO 3, LaCaMnO 3, LaCaCoO 3, LaCaCoFeO 3, LaNiFeO 3, at least one selected from the group consisting of _(LaSr) 2 NiO ₄ Conductive ceramic mainly composed of material, or mainly composed of at least one metal selected from the group consisting of Pt, Pd, Ag, Au, Ru, Rh, Ni, Fe, Cr and alloys composed mainly of these metals The solid oxide fuel cell according to any one of claims 1 to 6.

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